Hand-Held Power Tool and Protective Device for a Hand-Held Power Tool

ABSTRACT

A hand-held power tool has a housing and a drive motor arranged in the housing. A blower wheel is provided, wherein the housing has at least one area provided with openings allowing passage of air conveyed by the blower wheel. A protective device is arranged on an exterior wall of the housing, wherein the protective device has a damping area and the damping area protects the housing in the area provided with the openings from mechanical impact loads.

BACKGROUND OF THE INVENTION

The invention relates to a hand-held power tool comprising a drive motorthat is arranged in a housing of the power tool and further comprisingat least one blower wheel wherein the housing of the power tool has atleast one area provided with openings allowing passage of air conveyedby the blower wheel. The invention furthermore relates to a protectivedevice for a hand-held power tool.

U.S. 2001/0005482 A1 discloses a hand-held power tool in the form of ablower whose housing has intake ports. In the area of the intake ports,the structure of the housing is weakened. When making such a housingfrom plastic material, reinforcements and the like must be provided inorder to ensure a sufficient stability of the housing. A point impactload on the housing in the area of the intake ports can cause damage tothe housing.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a hand-held powertool of the aforementioned kind that is well protected from mechanicalloads. A further object of the invention resides in that a protectivedevice for protecting the housing of the hand-held power tool frommechanical loads is to be provided.

In accordance with the present invention, this is achieved in that onthe exterior wall of the housing a protective device is arranged thathas a damping area wherein the damping area protects the housing in thearea provided with openings from mechanical impact loads.

With regard to the protective device this object is solved in that theprotective device has a damping area for protecting a housing of thepower tool from mechanical loads and at least one attachment means forattaching the protective device on the housing of the power tool.

In order to be able to absorb mechanical loads on the housing such aspoint impact loads or the like, it is proposed to arrange on theexterior wall of the housing a protective device. The protective devicehas a damping area that protects mechanically the housing in the area ofthe openings. The damping area enables distribution of impact loadsacross a large area so that great point loads are prevented. At the sametime, impacts can be dampened and absorbed. The protective device canalso be retrofitted on already existing power tools.

It is provided that the blower wheel is a fan wheel that conveys coolingair to the drive motor. Alternatively or additionally, a blower wheelcan be provided that conveys working air of the power tool, inparticular, when the power tool is a blower, a vacuum device and/or asprayer. Through the openings air can be sucked in or blown out.

A protective device that has a damping area is particularly advantageousfor a power tool whose housing is provided in the area of the openingswith webs that separate the individual openings from one another. Suchwebs that are in particular arranged in a grid configuration cause aweakening of the structure of the housing. By means of the protectivedevice, a satisfactory stability of the housing in the weakened area canbe achieved without the webs having to be too large or having to be madefrom a stronger material. In particular the arrangement of theprotective device on an outwardly projecting area of the housing isadvantageous. An outwardly projecting area of the housing is susceptibleto mechanical loads that can occur when the housing hits other objectsor when the housing is dropped. These mechanical loads can be absorbedwell by the protective devices. In this way, the housing as a whole canbe produced with comparatively small wall thickness and thus minimalweight. This is advantageous in particular in the case of hand-heldpower tools because the operator must carry the entire weight of thepower tool.

Expediently, the drive motor is an internal combustion engine. It isprovided that the power tool has a starter device for the internalcombustion engine wherein the protective device is arranged in the areaof the starter device on the housing. In the area where the starterdevice is located there are usually also cooling air openings. Starterdevices that are manually actuated have usually a handle by means ofwhich a cable drum can be rotated. In order to ensure directtransmission of the force onto the cable drum, the starter device isusually arranged in an area of the housing that is located on theexterior and projects past the main body of the housing. This area istherefore not well protected from mechanical loads.

Advantageously, the damping area of the protective device is comprisedat least partially of an elastic material. Advantageously, the elasticmaterial is rubber or a thermoplastic elastomer. Elastic materials canabsorb impacts easily and distribute the impact well. In this way,overloading of the housing in individual areas is prevented. Suchelastic or flexible materials have a comparatively minimal weight sothat the housing including the protective device can be produced with aminimal weight in comparison to a housing that is so strong, i.e., hasthick walls and is provided with reinforcements so that high impactforces can be absorbed. In particular, the protective device iscomprised of a first material and a second material wherein the firstand second materials have different mechanical properties. In this way,the protective device can be matched well to the forces to be absorbed.It can be provided that the damping area of the protective device is ofa solid (no voids) configuration. It can also be advantageous that thedamping area of the protective device has at least one cavity. Bydesigning the cavities of the protective device in a suitable way, atargeted adjustment of the damping properties of the protective devicecan be achieved. By means of a suitable configuration of the cavities,it is also possible to provide through the cavities an elasticity orflexibility so that the material of the protective device itself musthave only minimal elasticity.

Advantageously, the protective device is detachably secured on thehousing. In this way, the protective device can be removed in case ofworking tasks in which the housing of the power tool is not subjected tohigh mechanical loads. In this way, the weight of the power tool isreduced for such tasks. Advantageously, the protective device is securedon the housing by a locking (snap-on) connection. Expediently, theprotective device has at least one locking finger that is locked in anopening of the housing. For fixation of the protective device, thealready existing openings can thus be used for this purpose. Additionaldevices for attachment must not be provided on the housing. However, itcan be provided that the protective device is secured on the housing byan adhesive connection. Advantageously, the protective device isinjection-molded onto the housing.

For a protective device for a hand-held power tool it is provided thatthe protective device has a damping area for protection of a housing ofthe power tool from mechanical loads as well as attachment means forattaching the protective device on the housing of the power tool. Theprotective device can be secured with the attachment means on thehousing of the power tool, in particular in such way that the protectivedevice protects an area of the housing of the power tool that is exposedto high mechanical loads or whose structure is weakened. Accordingly, ina simple way a protection of the housing of the power tool frommechanical loads and thus protection of the housing from damage can beachieved.

Advantageously, the attachment means provides for a releasableconnection. In this way, the protective device can be removed ordetached from the housing of the power tool when the power tool is to beused in such a way that it is exposed to only minimal mechanical loads.Depending on the type of use of the power tool, the protective devicecan be secured on the housing of the power tool or can be removed fromit. Advantageously, the attachment means comprises a locking hook. Thelocking hook is in particular arranged on a locking finger wherein thelocking finger is attached to the damping area. Advantageously, thedamping area is of an annular configuration. The annular configurationof the damping area enables the protection of a comparatively large areaof the power tool with little material being expended on the protectivedevice. In this way, the protective device can be of a simple andlightweight design. The damping area can be, for example, of a circularring shape or can be shaped as an oval ring.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective illustration of a blower.

FIG. 2 is a schematic section illustration of a blower.

FIG. 3 is a detail view of the blower of FIG. 1 in the area of thestarter device.

FIG. 4 shows the housing of the blower of FIG. 1 in the area of thestarter device.

FIG. 5 is a section view of the housing of the blower in the area of thestarter device in a simplified illustration.

FIG. 6 is a first perspective illustration of a protective deviceaccording to the invention.

FIG. 7 is a second perspective illustration of the protective deviceaccording to the invention.

FIG. 8 is a schematic section illustration of one embodiment of aprotective device according to the invention.

FIG. 9 is a schematic section illustration of another embodiment of aprotective device according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The hand-held portable power tool illustrated in FIG. 1 is a blower 1.However, the invention can also be used for other hand-held power toolssuch as vacuum devices, combined vacuum/blower devices, motor chainsaws,trimmers or the like. The blower 1 has a housing 2 on which a blowertube 3 is secured. The blower 1 conveys working air through the blowertube 3. For conveying the working air, the drive motor 7, schematicallyillustrated in FIG. 1, is arranged in the housing 2. The drive motor isan internal combustion engine. The drive motor 7 is in particular atwo-stroke engine, but the drive motor 7 can also be a four-strokeengine, in particular, a mixture-lubricated four-stroke engine.

On the housing 2 a top handle 4 for guiding the blower 1 is arranged. Onthe housing 2 there are two legs 6. The blower 1 can be put down to reston the two legs 6. For starting the drive motor 7, the blower 1 has astarter device 8. The starter device 8 has a starter handle 9 to whichis secured a cable, not illustrated, that when pulling the starterhandle 9 will cause the cable drum arranged in the housing 2 to rotateand thereby start the internal combustion engine provided as the drivemotor 7. The starter device 8 can however also be operated electrically.

A series of cooling air openings 15 is provided on the housing 2 in thearea adjacent to the blower tube 3 that points forwardly in operation aswell as in the area of the starter device 8.

In FIG. 2, the configuration of the blower 1 is schematically shown. Thedrive motor 7 has a crankshaft 10 that is driven in rotation by thereciprocating movement of the piston 11. The starter device 8 acts onthe crankshaft 10. Between the starter device 8 and the drive motor 7, ablower wheel 18 can be fixedly secured on the crankshaft 10. The blowerwheel 18 serves in this connection in particular for conveying coolingair to the drive motor 7. The cooling air is sucked in through thecooling air openings 15 (FIG. 1) arranged in the area of the starterdevice 8.

The blower 1 has a blower spiral 13 having secured to its exit theblower tube 3. The crankshaft 10 drives a second blower wheel 12 inrotation which is used for conveying working air through the blowerspiral 13 into the blower tube 3. The second blower wheel 12 takes inworking air in the axial direction through intake openings 14(schematically shown in FIG. 2).

FIGS. 3 and 4 show the area of the housing 2 where the starter device 8is located. In the area of the starter device 8 the housing 2 is curvedoutwardly in the shape of a truncated cone. The cone wall is providedwith cooling air openings 15. The cooling air openings 15 are separatedfrom one another in the circumferential direction by circumferentiallyextending webs 20 as well as radial webs 21. The characterization ascircumferential and radial refers in this connection to the axis ofrotation of the crankshaft 10. In the area of the starter device 8 onthe housing 2 a flat circular plate 23 is arranged. On the circumferenceof the circular plate 23 a protective device 16 is secured on thehousing 2. The protective device 16 has a damping area 28 that is of acircular annular shape in the embodiment. The damping area 28 forms anoutwardly projecting bead on the housing 2 so that the housing 2 in thearea of the starter device 8 is protected mechanically from externalimpacts. When the housing 2 hits a plane object, for example, when theblower 1 drops to the ground, in the area of the starter device 8 onlythe damping area 28 can contact the ground. The housing 2 itself isprotected in this area.

FIG. 5 shows the housing 2 in the area of the starter device 8 insection. The arrangement of the starter device 8 in the housing interior27 is schematically shown. The damping area 28 is arranged on theexterior 26 of the housing 2. The damping area 28 is supported withinwardly projecting lip 22 on the plate 23 of the housing 2. The dampingarea 28 is provided with a total of 10 locking fingers 19 (see alsoFIGS. 6 and 7). Each locking finger 19 has an outwardly projectinglocking hook 25 that engages a circumferential web 20. Each finger 19projects through a cooling air opening 15. The locking hooks 25 areaccessible from the exterior housing wall 26 of the housing 2 so thatthe locking hooks 25 can be pressed inwardly in order to release them.In this way, the protective device 16 can be removed or detached fromthe housing 2 if this is desired by the operator. On the damping area28, the protective device 16 has a circumferential shoulder 17 supportedon the housing 2. In this way, the protective device 16 is securedsafely on the housing 2.

As shown in FIGS. 6 and 7, the protective device 16 has an area 24 whereno locking fingers 19 are arranged. The area 24 will be positioned inthe area of the handle 9. The other locking fingers 19 are distributeduniformly about the circumference of the damping area 28.

The protective device 16 is comprised advantageously of an elastic orflexible material. In particular, the protective device 16 is comprisedof rubber or a thermoplastic elastomer. However, other materials mayalso be advantageous.

In FIG. 8, one embodiment of the protective device 36 is illustrated.The damping area 28 of the protective device 36 comprises a firstmaterial 37 that forms a base member. The first material 37 is securedon the housing 2 of the blower 1, in particular, by an adhesive. On thebase member formed by the first material 37 a second material 38 isprovided as a coating or cover. The second material 38 encloses thefirst material 37 in those areas where the protective device 16 willcome into contact with other flat objects. When the housing 2 of theblower 1 impacts on an object, first the second material 38 contacts theobject. The first material 37 and the second material 38 have differentmechanical properties, for example, the second material can be moreelastic and softer than the first material 37. By a suitable selectionof the materials and of the geometry of the materials, the desireddamping and springing properties can be adjusted.

In the embodiment illustrated in FIG. 9, the desired elasticity anddamping properties of the protective device 46 are achieved by selectinga suitable geometry. In order to increase the elasticity of theprotective device 46, the protective device 46 has at least one cavity47. It is also possible that several cavities 47 are distributed aboutthe circumference of the protective device 46. The cavities 47 can beopen toward the housing 2 or can be completely closed off. For fixationon the housing 2 it is provided that the protective device 46 isinjection-molded onto the housing 2. The protective device 46 iscomprised also of a material with elastic properties such as rubber or athermoplastic elastomer.

The aforementioned configurations for fixation of the protective deviceand for adjusting the elasticity of the protective device can becombined with one another in any way in order to achieve suitableproperties of the protective device. The openings for the passage of aircan also be openings through which the conveyed air is blown out, inparticular when the power tool is a vacuum device or a combinedvacuum/blower device.

The specification incorporates by reference the entire disclosure ofGerman priority document 10 2007 007 182.7 having a filing date of Feb.14, 2007.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the inventive principles, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles.

What is claimed is:
 1. A hand-held power tool comprising: a housing, adrive motor arranged in the housing; a first blower wheel, wherein thehousing has at least one area provided with openings allowing passage ofair conveyed by the first blower wheel; a protective device arranged onan exterior side of the housing, wherein the protective device has adamping area and the damping area protects the housing in the areaprovided with the openings from mechanical impact loads.
 2. The powertool according to claim 1, wherein the first blower wheel is a fan wheelthat conveys cooling air to the drive motor.
 3. The power tool accordingto claim 2, comprising a second blower wheel conveying working air ofthe power tool.
 4. The power tool according to claim 1, wherein thefirst blower wheel conveys working air of the power tool.
 5. The powertool according to claim 1, wherein the housing has webs in the areaprovided with the openings, wherein the webs separate the individualopenings from one another.
 6. The power tools according to claim 1,wherein the protective device is arranged on an area of the housing thatprojects outwardly.
 7. The power tool according to claim 1, wherein thedrive motor is an internal combustion engine and the power tool has astarter device for the internal combustion engine wherein the protectivedevice is arranged on the housing in the area where the starter deviceis located.
 8. The power tool according to claim 1, wherein the dampingarea of the protective device is at least partially comprised of anelastic material.
 9. The power to according to claim 8, wherein theelastic material is rubber or a thermoplastic elastomer.
 10. The powertool according to claim 1, wherein the protective device comprises afirst material and a second material and wherein the first material andthe second material have different mechanical properties.
 11. The powertool according to claim 1, wherein the damping area of the protectivedevice is solid.
 12. The power tool according to claim 1, wherein thedamping area of the protective device has at least one cavity.
 13. Thepower tool according to claim 1, wherein the protective device isdetachably secured on the housing.
 14. The power tool according to claim1, wherein the protective device is secured on the housing by a lockingconnection wherein the protective device has at least one locking fingerthat is locked in one of the openings of the housing.
 15. The power toolaccording to claim 1, wherein the protective device is secured on thehousing by an adhesive connection.
 16. The power tool according to claim1, wherein the protective device is injection-molded to the housing. 17.A protective device for a hand-held power tool, wherein the protectivedevice has a damping area for protecting a housing of the power toolfrom mechanical loads and at least one attachment means attaching theprotective device on the housing of the power tool.
 18. The protectivedevice according to claim 17, wherein the at least one attachment meansis releasable.
 19. The protective device according to claim 17, whereinthe at least one attachment means has at least one locking hook arrangedon a locking finger and wherein the locking finger is attached to thedamping area.
 20. The protective device according to claim 17, whereinthe damping area is annular.